1. Field of the Invention
This invention relates to electromagnetic irradiation of surfaces and, in particular, this invention relates to LED-emitted electromagnetic irradiation of surfaces from reflectors.
2. Background
Typically, parabolic or elliptical reflectors are used for directing radiation using reflective optics to achieve uniform or focused irradiance, respectively. Obviously, other irradiance patterns can be generated using more complex reflector geometries. However, the quality of focus or collimating irradiance is largely dependent on how well irradiance is concentrated at the focal point of the optic. The foregoing problem is illustrated in FIG. 1, exemplifying an elliptical reflector 100 and a radiant (arc) source 102. While the reflective optic could be any curved surface, generally elliptical (focusing) or parabolic (collimating) reflective optics is most common. While this discussion applies to several reflector system geometries, the elliptical reflector depicted in FIG. 1 is exemplified. In FIG. 1A, assuming a small point arc source placed at the focal point f1 of the elliptical reflector 100, emitted radiation, as exemplified by light rays 103, can be focused at a secondary focal point f2 to achieve a desirable discrete focal image 104. However, a very small translation along focusing direction h of the point arc source 102 away from the focal point f2 defocuses the image about the second focal point f2 as shown at 106.
Where the radiation source is linear, such as a fluorescent lamp, the reflector may be an elliptical trough or a portion of an ellipse. The optical center of the linear lamp is placed along a focal line of the trough reflector. For example, if the arc source 102 of FIGS. 1A and 1B is linear, f1 would be a cross-section of a line, rather than a point. This is shown in FIG. 2, where the point source is replaced with a linear radiation source 108 such as a linear fluorescent lamp or linear arc lamp. The linear radiation source 108 is positioned so that the axis of the linear source is positioned at the focal line f1 of the trough reflector. In the case that the trough reflector 110 is a portion of a reflective elliptical surface, irradiance from the source, as depicted by rays 116, is focused along line f2. In the case that the trough reflector is a reflective parabolic surface, the rays 116 would be spread to uniformly irradiate a plane containing line f2. Displacement of the linear radiation source along direction h from the focal line f1 of the trough would reduce either the focus of the source at f2 (elliptical surface) or the uniformity in the plane containing f2 (parabolic surface).